For the purpose of acquiring a driving state or the like of a driver in a vehicle, a technology has conventionally been known for detecting a visual line of a driver and the movement thereof.
For example, Japanese Laid-open Patent Publication No. H07-35543 discloses a technology that displays a marker for calibration in front of a driver in a case where a predetermined switch is pushed by the driver, and executes calibration for detection of a visual line based on a positional relationship between the driver and the marker that is acquired by causing the driver to gaze at such a marker.
However, in the conventional technology described above, an operation of a driver is needed for each calibration, and hence, there is a problem of steps that are complicated and cannot readily be executed.
Furthermore, for calibration, a driver is caused to take a posture for pushing the above-mentioned switch in vehicle interior, and hence, the calibration is executed in a posture different from a posture that is taken by the driver at time of normal driving. Hence, there is a difficulty in executing detection of a visual line of a driver in a running vehicle with high accuracy.